Olefin based polymers are widely used in various applications due to their being chemically inert, having low density, and low cost. Applications include adhesives, tie layers, films, fibers, and combinations thereof.
Olefin based polymers may be formed into various films, which may be laminated to, coated on, or co-extruded with various substrates. The film and the substrate may be combined with other materials to form a structure having a plurality of layers, each layer having a specific purpose. Packaging laminates, for example, may comprise a plurality of layers, such as a configurationally rigid core layer of paper or paperboard, an outer liquid-tight layer, an oxygen gas barrier such as a mid-layer of aluminum foil, and/or other layers depending on application needs.
To provide effective adhesion, it is important that good bonding strength or intimate integrity between the layers be achieved for most applications. However, relatively non-polar olefin based polymers do not normally adhere well to substrates which are more polar.
In addition, the set time of an adhesive may need to be within limits consistent with a proposed end use. Tailoring of an adhesive set time however may be accomplished at the expense of other attributes of an adhesive. For example, while inclusion of various forms of wax (e.g., polyethylene wax) may reduce a set time of an adhesive, the inclusion of a wax may also reduce or destroy adhesive properties in particular temperature ranges, and/or to particular substrates, especially polar substrates.
Adhesives are typically not heat stable, especially with respect to color over a period of time when the adhesive is heated at or above its melting point. Stability issues related to thermal degradation, including those related to bond strength and color body formation at elevated temperatures, may render various adhesives unfit for a variety of end uses.
There thus remains a need for an adhesive that will intimately bond to both polar and non-polar substrates, preferably one that exhibits a superior durability of bond strength under various temperature conditions at particular set times and in the presence of aggressive products, and that is heat stable at elevated temperatures.